The present invention relates generally to intake or exhaust valve actuators for engines and, more particularly, to a valve actuator assembly for continuously variable secondary opening of an engine valve for an internal combustion engine.
It is known to provide a valve train or valve actuator assembly for an engine such as an internal combustion engine of a vehicle such as a motor vehicle. Typically, the valve train includes one or more valves, a cam shaft having one or more cams, and a tappet contacting each cam and valve. Typically, engine valve actuation is accomplished via the engine-driven driven camshaft.
It is also known to provide a valve train for an internal combustion engine having a valve with an adjustable stroke or variable lift. In this patent, the adjustment of the stroke or lift of the valve takes place by an eccentric shaft, which displaces the supporting point of a transfer element disposed between each cam and each intake/exhaust valve, in which case the two eccentrics assigned to one cylinder are of a different geometry. The transfer element is formed by a valve lever, which is supported on the eccentric and is actuated by the cam, which valve lever, in turn, acts upon a rocker lever.
One disadvantage of some of these valve trains is that desired phasing is achieved via a camshaft phaser, which is unacceptable for high compression combustion systems, wherein each valve must be capable of having its own specifiable lift and phase setting. Another disadvantage of some of these valve trains is that they do not provide secondary opening of the engine valve. A further disadvantage of some of these valve trains is that the do not provide variable valve lift and phasing.
As a result, it is desirable to provide a valve actuator assembly for an engine that provides secondary opening of an engine valve. It is also desirable to provide a valve actuator assembly for an engine that has variable valve lift and phasing. It is further desirable to provide a valve actuator assembly for an engine having more than one degree-of-freedom to allow decoupling of lift and phasing for an engine valve. Therefore, there is a need in the art to provide a valve actuator assembly for an engine that meets these desires.
It is, therefore, one object of the present invention to provide a new valve actuator assembly for an engine.
It is another object of the present invention to provide a valve actuator assembly for an engine that has continuously variable secondary opening of an engine valve.
To achieve the foregoing objects, the present invention is a valve actuator assembly for an engine. The valve actuator assembly includes a movable engine valve. The valve actuator assembly also includes a movable roller finger follower contacting the engine valve, a rotatable cam, a first intermediate finger follower for contact with the roller finger follower and the cam, and a second intermediate finger follower for contact with the roller finger follower and the cam. The valve actuator assembly also includes at least one first actuator operatively cooperating with the first intermediate finger follower to position the first intermediate finger follower relative to the cam to move the roller finger follower to position the engine valve at either one of a desired lift and phasing for a primary opening of the engine valve. The valve actuator assembly includes at least one second actuator operatively cooperating with the second intermediate finger follower to position the second intermediate finger follower relative to the cam to move the roller finger follower to position the engine valve at either one of a desired lift and phasing for a secondary opening of the engine valve.
One advantage of the present invention is that a valve actuator assembly is provided for an engine for secondary opening of an engine valve. Another advantage of the present invention is that the valve actuator assembly has increased functionality, i.e., secondary opening of the engine valve with variable lift and phasing. Yet another advantage of the present invention is that the valve actuator assembly has precision and repeatability and does not suffer from temperature dependent fluid characteristics of hydraulic systems. A further advantage of the present invention is that the valve actuator assembly allows individual valve control for a high compression engine. Yet a further advantage of the present invention is that the valve actuator assembly has cam-based actuation that enables precise operation.